MANCHESTER, England (AP) Whatever the competition, whatever the level of opponent, Romelu Lukaku cannot stop scoring in his first season at Manchester United.

The Belgium striker kept up the impressive start to his United career by heading in the second goal in a 3-0 win over Basel on the opening night of the Champions League on Tuesday.

That's six goals in six games for United, across three competitions. He scored in the UEFA Super Cup against Real Madrid on his competitive debut, two goals on his first start in the Premier League, and now on his first appearance in the Champions League group stage.

Signed from Everton for at least 75 million pounds ($97 million) this offseason, that hefty transfer is looking money well spent.

"For a striker, it's important as their performances are many times analyzed by scoring or not scoring," Mourinho said. "But I am happy with his performances overall - scoring, not scoring."

The negative for Mourinho on a rainy night at Old Trafford, when Marouane Fellaini and Marcus Rashford also scored against an overwhelmed Swiss champion, was the sight of Paul Pogba hobbling off with an apparent left hamstring injury in the 19th minute.

Mourinho said he wasn't sure about the severity of the injury, but the France midfielder left Old Trafford on crutches. United's captain for the match in the absence of Antonio Valencia, Pogba had two short spells out with hamstring problems in the second half of last season.

Fellaini, on as a substitute for Pogba, opened the scoring with a close-range header in the 35th before Lukaku climbed between two defenders to nod home Daley Blind's left-wing cross in the 53rd.

With two goals with his right foot, two with his left foot and now two with his head, Lukaku is showing he is a complete center forward.

Rashford completed the win in the 84th minute, soon after coming on a substitute, when he scuffed a shot into the ground and over the goalkeeper from Fellaini's cross.

Mourinho said United, a three-time European champion, was back in its "natural habitat" after being absent from the Champions League last season. United only qualified for Europe's top competition by winning the Europa League in May and this was a gentle introduction to Group A, with Basel offering little resistance.

"We can learn from this, and this is what I told my team at the final whistle," Basel manager Raphael Wicky said. "This team was suffering together, fighting together ... but what I didn't like at the beginning was I saw a team that was quite scared."

A few flicks and tricks failed to come off for United in the second half and Mourinho criticized his players for relaxing too much, saying: "We were playing fantasy football, Playstation football. I don't like it."

United looks to be the team to beat in Group A, which also contains Benfica and CSKA Moscow, but Mourinho won't be taking it easy.

"For the Real Madrids, Barcelonas and Bayern Munichs, the Champions League starts in February. Now is just the warming up," he said. "I think we are in the second level. The second level is, let's qualify, let's make the points to qualify for the knockout phase.

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